Method and apparatus for conditional handover based on the service time of candidate cells in a wireless communication system

ABSTRACT

A method and apparatus for conditional handover based on the service time of candidate cells in a wireless communication system is provided. A wireless device receives, from a network, handover configuration including information related to candidate cells to be measured and service time of each of the candidate cells. A wireless device performs measurement on the candidate cells. A wireless device selects a cell among the candidate cells based on the service time of each of the candidate cells. A wireless device performs handover to the selected cell.

TECHNICAL FIELD

The present disclosure relates to a method and apparatus for conditionalhandover based on the service time of candidate cells in a wirelesscommunication system.

RELATED ART

3rd generation partnership project (3GPP) long-term evolution (LTE) is atechnology for enabling high-speed packet communications. Many schemeshave been proposed for the LTE objective including those that aim toreduce user and provider costs, improve service quality, and expand andimprove coverage and system capacity. The 3GPP LTE requires reduced costper bit, increased service availability, flexible use of a frequencyband, a simple structure, an open interface, and adequate powerconsumption of a terminal as an upper-level requirement.

Work has started in international telecommunication union (ITU) and 3GPPto develop requirements and specifications for new radio (NR) systems.3GPP has to identify and develop the technology components needed forsuccessfully standardizing the new RAT timely satisfying both the urgentmarket needs, and the more long-term requirements set forth by the ITUradio communication sector (ITU-R) international mobiletelecommunications (IMT)-2020 process. Further, the NR should be able touse any spectrum band ranging at least up to 100 GHz that may be madeavailable for wireless communications even in a more distant future.

The NR targets a single technical framework addressing all usagescenarios, requirements and deployment scenarios including enhancedmobile broadband (eMBB), massive machine-type-communications (mMTC),ultra-reliable and low latency communications (URLLC), etc. The NR shallbe inherently forward compatible.

Thanks to the wide service coverage capabilities and reducedvulnerability of space/airborne vehicles to physical attacks and naturaldisasters, non-terrestrial networks (NTN) are expected to:

-   -   foster the roll out of 5G service in un-served areas that cannot        be covered by terrestrial 5G network (isolated/remote areas, on        board aircrafts or vessels) and underserved areas (e.g.,        sub-urban/rural areas) to upgrade the performance of limited        terrestrial networks in cost effective manner,    -   reinforce the 5G service reliability by providing service        continuity for machine-to-machine (M2M)/Internet-of-things (IoT)        devices or for passengers on board moving platforms (e.g.,        passenger vehicles-aircraft, ships, high speed trains, bus) or        ensuring service availability anywhere especially for critical        communications, future railway/maritime/aeronautical        communications, and to    -   enable 5G network scalability by providing efficient        multicast/broadcast resources for data delivery towards the        network edges or even user terminal.

SUMMARY

In 5th generation (5G) communication system, it is being discussed tointroduce conditional mobility. One example of conditional mobility isconditional handover (CHO). The conditional handover is essentially anetwork-configured but user equipment (UE)-controlled downlink mobilitymechanism with a potential to reduce the interruption time and handoverfailure/radio link failure. The conditional handover improves thehandover robustness significantly.

Due to nature of NTN (for example, NTN served by Low Earth orbit (LEO)satellites), a current conditional handover mechanism should beaddressed and/or discussed.

In an aspect, a method performed by a wireless device in a wirelesscommunication system is provided. A wireless device receives, from anetwork, handover configuration including information related tocandidate cells to be measured and service time of each of the candidatecells. A wireless device performs measurement on the candidate cells. Awireless device selects a cell among the candidate cells based on theservice time of each of the candidate cells. A wireless device performshandover to the selected cell.

In another aspect, a wireless device in a wireless communication systemis provided. A wireless device includes a transceiver, a memory, atleast one processor operatively coupled to the transceiver and thememory. The at least one processor is configured to control thetransceiver to receive, from a network, handover configuration includinginformation related to candidate cells to be measured and service timeof each of the candidate cells. The at least one processor is configuredto perform measurement on the candidate cells. The at least oneprocessor is configured to select a cell among the candidate cells basedon the service time of each of the candidate cells. The at least oneprocessor is configured to perform handover to the selected cell.

The present disclosure can have various advantageous effects.

According to some embodiments of the present disclosure, a wirelessdevice may perform conditional handover to the NTN cell efficiently.

For example, a wireless device may consider the available service timeas one condition of the conditional handover.

For example, a wireless device could select a cell, based on theavailable service time when at least two candidate cells meet theconfigured condition.

For example, a wireless device could determine a cell having the longestavailable service time among the candidate cells.

For example, a wireless device could select a cell having the longestservice time among the candidate cells.

Advantageous effects which can be obtained through specific embodimentsof the present disclosure are not limited to the advantageous effectslisted above. For example, there may be a variety of technical effectsthat a person having ordinary skill in the related art can understandand/or derive from the present disclosure. Accordingly, the specificeffects of the present disclosure are not limited to those explicitlydescribed herein, but may include various effects that may be understoodor derived from the technical features of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a communication system to whichimplementations of the present disclosure is applied.

FIG. 2 shows an example of wireless devices to which implementations ofthe present disclosure is applied.

FIG. 3 shows an example of a wireless device to which implementations ofthe present disclosure is applied.

FIG. 4 shows another example of wireless devices to whichimplementations of the present disclosure is applied.

FIG. 5 shows an example of UE to which implementations of the presentdisclosure is applied.

FIGS. 6 and 7 show an example of protocol stacks in a 3GPP basedwireless communication system to which implementations of the presentdisclosure is applied.

FIG. 8 shows a frame structure in a 3GPP based wireless communicationsystem to which implementations of the present disclosure is applied.

FIG. 9 shows a data flow example in the 3GPP NR system to whichimplementations of the present disclosure is applied.

FIG. 10 shows an example of satellite access network (without ISL) witha service link operating in frequency bands above 6 GHz allocated tofixed and mobile satellite services (FSS and MSS) to whichimplementations of the present disclosure is applied.

FIG. 11 shows an example of satellite access network (with ISL) with aservice link operating in frequency bands above 6 GHz allocated to FSSand MSS to which implementations of the present disclosure is applied.

FIG. 12 shows an example of satellite access network with a service linkoperating in frequency bands below 6 GHz allocated to MSS to whichimplementations of the present disclosure is applied.

FIG. 13 shows an example of satellite access network which service linkoperates below 6 GHz frequency bands allocated to MSS and complementedwith the terrestrial access network served by the same or independentcore networks to which implementations of the present disclosure isapplied.

FIG. 14 shows an example of overall procedure for condition basedautonomous handover procedure to which implementations of the presentdisclosure is applied.

FIG. 15 shows an example of a method for conditional handover based onthe service time of candidate cells in a wireless communication system,according to some embodiments of the present disclosure.

FIG. 16 shows an example of a method for conditional handover based onthe service time of candidate cells in a wireless communication system,according to some embodiments of the present disclosure.

FIG. 17 shows a diagram of an example of method for conditional handoverbased on the service time of candidate cells in a wireless communicationsystem, according to some embodiments of the present disclosure.

DESCRIPTION

The following techniques, apparatuses, and systems may be applied to avariety of wireless multiple access systems. Examples of the multipleaccess systems include a code division multiple access (CDMA) system, afrequency division multiple access (FDMA) system, a time divisionmultiple access (TDMA) system, an orthogonal frequency division multipleaccess (OFDMA) system, a single carrier frequency division multipleaccess (SC-FDMA) system, and a multicarrier frequency division multipleaccess (MC-FDMA) system. CDMA may be embodied through radio technologysuch as universal terrestrial radio access (UTRA) or CDMA2000. TDMA maybe embodied through radio technology such as global system for mobilecommunications (GSM), general packet radio service (GPRS), or enhanceddata rates for GSM evolution (EDGE). OFDMA may be embodied through radiotechnology such as institute of electrical and electronics engineers(IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or evolved UTRA(E-UTRA). UTRA is a part of a universal mobile telecommunications system(UMTS). 3rd generation partnership project (3GPP) long term evolution(LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employsOFDMA in DL and SC-FDMA in UL. LTE-advanced (LTE-A) is an evolvedversion of 3GPP LTE.

For convenience of description, implementations of the presentdisclosure are mainly described in regards to a 3GPP based wirelesscommunication system. However, the technical features of the presentdisclosure are not limited thereto. For example, although the followingdetailed description is given based on a mobile communication systemcorresponding to a 3GPP based wireless communication system, aspects ofthe present disclosure that are not limited to 3GPP based wirelesscommunication system are applicable to other mobile communicationsystems.

For terms and technologies which are not specifically described amongthe terms of and technologies employed in the present disclosure, thewireless communication standard documents published before the presentdisclosure may be referenced.

In the present disclosure, “A or B” may mean “only A”, “only B”, or“both A and B”. In other words, “A or B” in the present disclosure maybe interpreted as “A and/or B”. For example, “A, B or C” in the presentdisclosure may mean “only A”, “only B”, “only C”, or “any combination ofA, B and C”.

In the present disclosure, slash (/) or comma (,) may mean “and/or”. Forexample, “A/B” may mean “A and/or B”. Accordingly, “A/B” may mean “onlyA”, “only B”, or “both A and B”. For example, “A, B, C” may mean “A, Bor C”.

In the present disclosure, “at least one of A and B” may mean “only A”,“only B” or “both A and B”. In addition, the expression “at least one ofA or B” or “at least one of A and/or B” in the present disclosure may beinterpreted as same as “at least one of A and B”.

In addition, in the present disclosure, “at least one of A, B and C” maymean “only A”, “only B”, “only C”, or “any combination of A, B and C”.In addition, “at least one of A, B or C” or “at least one of A, B and/orC” may mean “at least one of A, B and C”.

Also, parentheses used in the present disclosure may mean “for example”.In detail, when it is shown as “control information (PDCCH)”, “PDCCH”may be proposed as an example of “control information”. In other words,“control information” in the present disclosure is not limited to“PDCCH”, and “PDDCH” may be proposed as an example of “controlinformation”. In addition, even when shown as “control information(i.e., PDCCH)”, “PDCCH” may be proposed as an example of “controlinformation”.

Technical features that are separately described in one drawing in thepresent disclosure may be implemented separately or simultaneously.

Although not limited thereto, various descriptions, functions,procedures, suggestions, methods and/or operational flowcharts of thepresent disclosure disclosed herein can be applied to various fieldsrequiring wireless communication and/or connection (e.g., 5G) betweendevices.

Hereinafter, the present disclosure will be described in more detailwith reference to drawings. The same reference numerals in the followingdrawings and/or descriptions may refer to the same and/or correspondinghardware blocks, software blocks, and/or functional blocks unlessotherwise indicated.

FIG. 1 shows an example of a communication system to whichimplementations of the present disclosure is applied.

The 5G usage scenarios shown in FIG. 1 are only exemplary, and thetechnical features of the present disclosure can be applied to other 5Gusage scenarios which are not shown in FIG. 1.

Three main requirement categories for 5G include (1) a category ofenhanced mobile broadband (eMBB), (2) a category of massive machine typecommunication (mMTC), and (3) a category of ultra-reliable and lowlatency communications (URLLC).

Partial use cases may require a plurality of categories for optimizationand other use cases may focus only upon one key performance indicator(KPI). 5G supports such various use cases using a flexible and reliablemethod.

eMBB far surpasses basic mobile Internet access and covers abundantbidirectional work and media and entertainment applications in cloud andaugmented reality. Data is one of 5G core motive forces and, in a 5Gera, a dedicated voice service may not be provided for the first time.In 5G, it is expected that voice will be simply processed as anapplication program using data connection provided by a communicationsystem. Main causes for increased traffic volume are due to an increasein the size of content and an increase in the number of applicationsrequiring high data transmission rate. A streaming service (of audio andvideo), conversational video, and mobile Internet access will be morewidely used as more devices are connected to the Internet. These manyapplication programs require connectivity of an always turned-on statein order to push real-time information and alarm for users. Cloudstorage and applications are rapidly increasing in a mobilecommunication platform and may be applied to both work andentertainment. The cloud storage is a special use case which acceleratesgrowth of uplink data transmission rate. 5G is also used for remote workof cloud. When a tactile interface is used, 5G demands much lowerend-to-end latency to maintain user good experience. Entertainment, forexample, cloud gaming and video streaming, is another core element whichincreases demand for mobile broadband capability. Entertainment isessential for a smartphone and a tablet in any place including highmobility environments such as a train, a vehicle, and an airplane. Otheruse cases are augmented reality for entertainment and informationsearch. In this case, the augmented reality requires very low latencyand instantaneous data volume.

In addition, one of the most expected 5G use cases relates a functioncapable of smoothly connecting embedded sensors in all fields, i.e.,mMTC. It is expected that the number of potential Internet-of-things(IoT) devices will reach 204 hundred million up to the year of 2020. Anindustrial IoT is one of categories of performing a main role enabling asmart city, asset tracking, smart utility, agriculture, and securityinfrastructure through 5G.

URLLC includes a new service that will change industry through remotecontrol of main infrastructure and an ultra-reliable/availablelow-latency link such as a self-driving vehicle. A level of reliabilityand latency is essential to control a smart grid, automatize industry,achieve robotics, and control and adjust a drone.

5G is a means of providing streaming evaluated as a few hundred megabitsper second to gigabits per second and may complement fiber-to-the-home(FTTH) and cable-based broadband (or DOCSIS). Such fast speed is neededto deliver TV in resolution of 4K or more (6K, 8K, and more), as well asvirtual reality and augmented reality. Virtual reality (VR) andaugmented reality (AR) applications include almost immersive sportsgames. A specific application program may require a special networkconfiguration. For example, for VR games, gaming companies need toincorporate a core server into an edge network server of a networkoperator in order to minimize latency.

Automotive is expected to be a new important motivated force in 5Gtogether with many use cases for mobile communication for vehicles. Forexample, entertainment for passengers requires high simultaneouscapacity and mobile broadband with high mobility. This is because futureusers continue to expect connection of high quality regardless of theirlocations and speeds. Another use case of an automotive field is an ARdashboard. The AR dashboard causes a driver to identify an object in thedark in addition to an object seen from a front window and displays adistance from the object and a movement of the object by overlappinginformation talking to the driver. In the future, a wireless moduleenables communication between vehicles, information exchange between avehicle and supporting infrastructure, and information exchange betweena vehicle and other connected devices (e.g., devices accompanied by apedestrian). A safety system guides alternative courses of a behavior sothat a driver may drive more safely drive, thereby lowering the dangerof an accident. The next stage will be a remotely controlled orself-driven vehicle. This requires very high reliability and very fastcommunication between different self-driven vehicles and between avehicle and infrastructure. In the future, a self-driven vehicle willperform all driving activities and a driver will focus only uponabnormal traffic that the vehicle cannot identify. Technicalrequirements of a self-driven vehicle demand ultra-low latency andultra-high reliability so that traffic safety is increased to a levelthat cannot be achieved by human being.

A smart city and a smart home/building mentioned as a smart society willbe embedded in a high-density wireless sensor network. A distributednetwork of an intelligent sensor will identify conditions for costs andenergy-efficient maintenance of a city or a home. Similar configurationsmay be performed for respective households. All of temperature sensors,window and heating controllers, burglar alarms, and home appliances arewirelessly connected. Many of these sensors are typically low in datatransmission rate, power, and cost. However, real-time HD video may bedemanded by a specific type of device to perform monitoring.

Consumption and distribution of energy including heat or gas isdistributed at a higher level so that automated control of thedistribution sensor network is demanded. The smart grid collectsinformation and connects the sensors to each other using digitalinformation and communication technology so as to act according to thecollected information. Since this information may include behaviors of asupply company and a consumer, the smart grid may improve distributionof fuels such as electricity by a method having efficiency, reliability,economic feasibility, production sustainability, and automation. Thesmart grid may also be regarded as another sensor network having lowlatency.

Mission critical application (e.g., e-health) is one of 5G usescenarios. A health part contains many application programs capable ofenjoying benefit of mobile communication. A communication system maysupport remote treatment that provides clinical treatment in a farawayplace. Remote treatment may aid in reducing a barrier against distanceand improve access to medical services that cannot be continuouslyavailable in a faraway rural area. Remote treatment is also used toperform important treatment and save lives in an emergency situation.The wireless sensor network based on mobile communication may provideremote monitoring and sensors for parameters such as heart rate andblood pressure.

Wireless and mobile communication gradually becomes important in thefield of an industrial application. Wiring is high in installation andmaintenance cost. Therefore, a possibility of replacing a cable withreconstructible wireless links is an attractive opportunity in manyindustrial fields. However, in order to achieve this replacement, it isnecessary for wireless connection to be established with latency,reliability, and capacity similar to those of the cable and managementof wireless connection needs to be simplified. Low latency and a verylow error probability are new requirements when connection to 5G isneeded.

Logistics and freight tracking are important use cases for mobilecommunication that enables inventory and package tracking anywhere usinga location-based information system.

The use cases of logistics and freight typically demand low data ratebut require location information with a wide range and reliability.

Referring to FIG. 1, the communication system 1 includes wirelessdevices 100 a to 100 f, base stations (BSs) 200, and a network 300.Although FIG. 1 illustrates a 5G network as an example of the network ofthe communication system 1, the implementations of the presentdisclosure are not limited to the 5G system, and can be applied to thefuture communication system beyond the 5G system.

The BSs 200 and the network 300 may be implemented as wireless devicesand a specific wireless device may operate as a BS/network node withrespect to other wireless devices.

The wireless devices 100 a to 100 f represent devices performingcommunication using radio access technology (RAT) (e.g., 5G new RAT(NR)) or LTE) and may be referred to as communication/radio/5G devices.The wireless devices 100 a to 100 f may include, without being limitedto, a robot 100 a, vehicles 100 b-1 and 100 b-2, an extended reality(XR) device 100 c, a hand-held device 100 d, a home appliance 100 e, anIoT device 100 f, and an artificial intelligence (AI) device/server 400.For example, the vehicles may include a vehicle having a wirelesscommunication function, an autonomous driving vehicle, and a vehiclecapable of performing communication between vehicles. The vehicles mayinclude an unmanned aerial vehicle (UAV) (e.g., a drone). The XR devicemay include an AR/VR/Mixed Reality (MR) device and may be implemented inthe form of a head-mounted device (HMD), a head-up display (HUD) mountedin a vehicle, a television, a smartphone, a computer, a wearable device,a home appliance device, a digital signage, a vehicle, a robot, etc. Thehand-held device may include a smartphone, a smartpad, a wearable device(e.g., a smartwatch or a smartglasses), and a computer (e.g., anotebook). The home appliance may include a TV, a refrigerator, and awashing machine. The IoT device may include a sensor and a smartmeter.

In the present disclosure, the wireless devices 100 a to 100 f may becalled user equipments (UEs). A UE may include, for example, a cellularphone, a smartphone, a laptop computer, a digital broadcast terminal, apersonal digital assistant (PDA), a portable multimedia player (PMP), anavigation system, a slate personal computer (PC), a tablet PC, anultrabook, a vehicle, a vehicle having an autonomous traveling function,a connected car, an UAV, an AI module, a robot, an AR device, a VRdevice, an MR device, a hologram device, a public safety device, an MTCdevice, an IoT device, a medical device, a FinTech device (or afinancial device), a security device, a weather/environment device, adevice related to a 5G service, or a device related to a fourthindustrial revolution field.

The UAV may be, for example, an aircraft aviated by a wireless controlsignal without a human being onboard.

The VR device may include, for example, a device for implementing anobject or a background of the virtual world. The AR device may include,for example, a device implemented by connecting an object or abackground of the virtual world to an object or a background of the realworld. The MR device may include, for example, a device implemented bymerging an object or a background of the virtual world into an object ora background of the real world. The hologram device may include, forexample, a device for implementing a stereoscopic image of 360 degreesby recording and reproducing stereoscopic information, using aninterference phenomenon of light generated when two laser lights calledholography meet.

The public safety device may include, for example, an image relay deviceor an image device that is wearable on the body of a user.

The MTC device and the IoT device may be, for example, devices that donot require direct human intervention or manipulation. For example, theMTC device and the IoT device may include smartmeters, vending machines,thermometers, smartbulbs, door locks, or various sensors.

The medical device may be, for example, a device used for the purpose ofdiagnosing, treating, relieving, curing, or preventing disease. Forexample, the medical device may be a device used for the purpose ofdiagnosing, treating, relieving, or correcting injury or impairment. Forexample, the medical device may be a device used for the purpose ofinspecting, replacing, or modifying a structure or a function. Forexample, the medical device may be a device used for the purpose ofadjusting pregnancy. For example, the medical device may include adevice for treatment, a device for operation, a device for (in vitro)diagnosis, a hearing aid, or a device for procedure.

The security device may be, for example, a device installed to prevent adanger that may arise and to maintain safety. For example, the securitydevice may be a camera, a closed-circuit TV (CCTV), a recorder, or ablack box.

The FinTech device may be, for example, a device capable of providing afinancial service such as mobile payment. For example, the FinTechdevice may include a payment device or a point of sales (POS) system.

The weather/environment device may include, for example, a device formonitoring or predicting a weather/environment.

The wireless devices 100 a to 100 f may be connected to the network 300via the BSs 200. An AI technology may be applied to the wireless devices100 a to 100 f and the wireless devices 100 a to 100 f may be connectedto the AI server 400 via the network 300. The network 300 may beconfigured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR)network, and a beyond-5G network. Although the wireless devices 100 a to100 f may communicate with each other through the BSs 200/network 300,the wireless devices 100 a to 100 f may perform direct communication(e.g., sidelink communication) with each other without passing throughthe BSs 200/network 300. For example, the vehicles 100 b-1 and 100 b-2may perform direct communication (e.g., vehicle-to-vehicle(V2V)/vehicle-to-everything (V2X) communication). The IoT device (e.g.,a sensor) may perform direct communication with other IoT devices (e.g.,sensors) or other wireless devices 100 a to 100 f.

Wireless communication/connections 150 a, 150 b and 150 c may beestablished between the wireless devices 100 a to 100 f and/or betweenwireless device 100 a to 100 f and BS 200 and/or between BSs 200.Herein, the wireless communication/connections may be establishedthrough various RATs (e.g., 5G NR) such as uplink/downlink communication150 a, sidelink communication (or device-to-device (D2D) communication)150 b, inter-base station communication 150 c (e.g., relay, integratedaccess and backhaul (IAB)), etc. The wireless devices 100 a to 100 f andthe BSs 200/the wireless devices 100 a to 100 f may transmit/receiveradio signals to/from each other through the wirelesscommunication/connections 150 a, 150 b and 150 c. For example, thewireless communication/connections 150 a, 150 b and 150 c maytransmit/receive signals through various physical channels. To this end,at least a part of various configuration information configuringprocesses, various signal processing processes (e.g., channelencoding/decoding, modulation/demodulation, and resourcemapping/de-mapping), and resource allocating processes, fortransmitting/receiving radio signals, may be performed based on thevarious proposals of the present disclosure.

FIG. 2 shows an example of wireless devices to which implementations ofthe present disclosure is applied.

Referring to FIG. 2, a first wireless device 100 and a second wirelessdevice 200 may transmit/receive radio signals to/from an external devicethrough a variety of RATs (e.g., LTE and NR). In FIG. 2, {the firstwireless device 100 and the second wireless device 200} may correspondto at least one of {the wireless device 100 a to 100 f and the BS 200},{the wireless device 100 a to 100 f and the wireless device 100 a to 100f} and/or {the BS 200 and the BS 200} of FIG. 1.

The first wireless device 100 may include one or more processors 102 andone or more memories 104 and additionally further include one or moretransceivers 106 and/or one or more antennas 108. The processor(s) 102may control the memory(s) 104 and/or the transceiver(s) 106 and may beconfigured to implement the descriptions, functions, procedures,suggestions, methods and/or operational flowcharts described in thepresent disclosure. For example, the processor(s) 102 may processinformation within the memory(s) 104 to generate firstinformation/signals and then transmit radio signals including the firstinformation/signals through the transceiver(s) 106. The processor(s) 102may receive radio signals including second information/signals throughthe transceiver(s) 106 and then store information obtained by processingthe second information/signals in the memory(s) 104. The memory(s) 104may be connected to the processor(s) 102 and may store a variety ofinformation related to operations of the processor(s) 102. For example,the memory(s) 104 may store software code including commands forperforming a part or the entirety of processes controlled by theprocessor(s) 102 or for performing the descriptions, functions,procedures, suggestions, methods and/or operational flowcharts describedin the present disclosure. Herein, the processor(s) 102 and thememory(s) 104 may be a part of a communication modem/circuit/chipdesigned to implement RAT (e.g., LTE or NR). The transceiver(s) 106 maybe connected to the processor(s) 102 and transmit and/or receive radiosignals through one or more antennas 108. Each of the transceiver(s) 106may include a transmitter and/or a receiver. The transceiver(s) 106 maybe interchangeably used with radio frequency (RF) unit(s). In thepresent disclosure, the first wireless device 100 may represent acommunication modem/circuit/chip.

The second wireless device 200 may include one or more processors 202and one or more memories 204 and additionally further include one ormore transceivers 206 and/or one or more antennas 208. The processor(s)202 may control the memory(s) 204 and/or the transceiver(s) 206 and maybe configured to implement the descriptions, functions, procedures,suggestions, methods and/or operational flowcharts described in thepresent disclosure. For example, the processor(s) 202 may processinformation within the memory(s) 204 to generate thirdinformation/signals and then transmit radio signals including the thirdinformation/signals through the transceiver(s) 206. The processor(s) 202may receive radio signals including fourth information/signals throughthe transceiver(s) 106 and then store information obtained by processingthe fourth information/signals in the memory(s) 204. The memory(s) 204may be connected to the processor(s) 202 and may store a variety ofinformation related to operations of the processor(s) 202. For example,the memory(s) 204 may store software code including commands forperforming a part or the entirety of processes controlled by theprocessor(s) 202 or for performing the descriptions, functions,procedures, suggestions, methods and/or operational flowcharts describedin the present disclosure. Herein, the processor(s) 202 and thememory(s) 204 may be a part of a communication modem/circuit/chipdesigned to implement RAT (e.g., LTE or NR). The transceiver(s) 206 maybe connected to the processor(s) 202 and transmit and/or receive radiosignals through one or more antennas 208. Each of the transceiver(s) 206may include a transmitter and/or a receiver. The transceiver(s) 206 maybe interchangeably used with RF unit(s). In the present disclosure, thesecond wireless device 200 may represent a communicationmodem/circuit/chip.

Hereinafter, hardware elements of the wireless devices 100 and 200 willbe described more specifically. One or more protocol layers may beimplemented by, without being limited to, one or more processors 102 and202. For example, the one or more processors 102 and 202 may implementone or more layers (e.g., functional layers such as physical (PHY)layer, media access control (MAC) layer, radio link control (RLC) layer,packet data convergence protocol (PDCP) layer, radio resource control(RRC) layer, and service data adaptation protocol (SDAP) layer). The oneor more processors 102 and 202 may generate one or more protocol dataunits (PDUs) and/or one or more service data unit (SDUs) according tothe descriptions, functions, procedures, suggestions, methods and/oroperational flowcharts disclosed in the present disclosure. The one ormore processors 102 and 202 may generate messages, control information,data, or information according to the descriptions, functions,procedures, suggestions, methods and/or operational flowcharts disclosedin the present disclosure. The one or more processors 102 and 202 maygenerate signals (e.g., baseband signals) including PDUs, SDUs,messages, control information, data, or information according to thedescriptions, functions, procedures, suggestions, methods and/oroperational flowcharts disclosed in the present disclosure and providethe generated signals to the one or more transceivers 106 and 206. Theone or more processors 102 and 202 may receive the signals (e.g.,baseband signals) from the one or more transceivers 106 and 206 andacquire the PDUs, SDUs, messages, control information, data, orinformation according to the descriptions, functions, procedures,suggestions, methods and/or operational flowcharts disclosed in thepresent disclosure.

The one or more processors 102 and 202 may be referred to ascontrollers, microcontrollers, microprocessors, or microcomputers. Theone or more processors 102 and 202 may be implemented by hardware,firmware, software, or a combination thereof. As an example, one or moreapplication specific integrated circuits (ASICs), one or more digitalsignal processors (DSPs), one or more digital signal processing devices(DSPDs), one or more programmable logic devices (PLDs), or one or morefield programmable gate arrays (FPGAs) may be included in the one ormore processors 102 and 202. descriptions, functions, procedures,suggestions, methods and/or operational flowcharts disclosed in thepresent disclosure may be implemented using firmware or software and thefirmware or software may be configured to include the modules,procedures, or functions. Firmware or software configured to perform thedescriptions, functions, procedures, suggestions, methods and/oroperational flowcharts disclosed in the present disclosure may beincluded in the one or more processors 102 and 202 or stored in the oneor more memories 104 and 204 so as to be driven by the one or moreprocessors 102 and 202. The descriptions, functions, procedures,suggestions, methods and/or operational flowcharts disclosed in thepresent disclosure may be implemented using firmware or software in theform of code, commands, and/or a set of commands.

The one or more memories 104 and 204 may be connected to the one or moreprocessors 102 and 202 and store various types of data, signals,messages, information, programs, code, instructions, and/or commands.The one or more memories 104 and 204 may be configured by read-onlymemories (ROMs), random access memories (RAMs), electrically erasableprogrammable read-only memories (EPROMs), flash memories, hard drives,registers, cash memories, computer-readable storage media, and/orcombinations thereof. The one or more memories 104 and 204 may belocated at the interior and/or exterior of the one or more processors102 and 202. The one or more memories 104 and 204 may be connected tothe one or more processors 102 and 202 through various technologies suchas wired or wireless connection.

The one or more transceivers 106 and 206 may transmit user data, controlinformation, and/or radio signals/channels, mentioned in thedescriptions, functions, procedures, suggestions, methods and/oroperational flowcharts disclosed in the present disclosure, to one ormore other devices. The one or more transceivers 106 and 206 may receiveuser data, control information, and/or radio signals/channels, mentionedin the descriptions, functions, procedures, suggestions, methods and/oroperational flowcharts disclosed in the present disclosure, from one ormore other devices. For example, the one or more transceivers 106 and206 may be connected to the one or more processors 102 and 202 andtransmit and receive radio signals. For example, the one or moreprocessors 102 and 202 may perform control so that the one or moretransceivers 106 and 206 may transmit user data, control information, orradio signals to one or more other devices. The one or more processors102 and 202 may perform control so that the one or more transceivers 106and 206 may receive user data, control information, or radio signalsfrom one or more other devices.

The one or more transceivers 106 and 206 may be connected to the one ormore antennas 108 and 208 and the one or more transceivers 106 and 206may be configured to transmit and receive user data, controlinformation, and/or radio signals/channels, mentioned in thedescriptions, functions, procedures, suggestions, methods and/oroperational flowcharts disclosed in the present disclosure, through theone or more antennas 108 and 208. In the present disclosure, the one ormore antennas may be a plurality of physical antennas or a plurality oflogical antennas (e.g., antenna ports).

The one or more transceivers 106 and 206 may convert received radiosignals/channels, etc., from RF band signals into baseband signals inorder to process received user data, control information, radiosignals/channels, etc., using the one or more processors 102 and 202.The one or more transceivers 106 and 206 may convert the user data,control information, radio signals/channels, etc., processed using theone or more processors 102 and 202 from the base band signals into theRF band signals. To this end, the one or more transceivers 106 and 206may include (analog) oscillators and/or filters. For example, thetransceivers 106 and 206 can up-convert OFDM baseband signals to acarrier frequency by their (analog) oscillators and/or filters under thecontrol of the processors 102 and 202 and transmit the up-converted OFDMsignals at the carrier frequency. The transceivers 106 and 206 mayreceive OFDM signals at a carrier frequency and down-convert the OFDMsignals into OFDM baseband signals by their (analog) oscillators and/orfilters under the control of the transceivers 102 and 202.

In the implementations of the present disclosure, a UE may operate as atransmitting device in uplink (UL) and as a receiving device in downlink(DL). In the implementations of the present disclosure, a BS may operateas a receiving device in UL and as a transmitting device in DL.Hereinafter, for convenience of description, it is mainly assumed thatthe first wireless device 100 acts as the UE, and the second wirelessdevice 200 acts as the BS. For example, the processor(s) 102 connectedto, mounted on or launched in the first wireless device 100 may beconfigured to perform the UE behavior according to an implementation ofthe present disclosure or control the transceiver(s) 106 to perform theUE behavior according to an implementation of the present disclosure.The processor(s) 202 connected to, mounted on or launched in the secondwireless device 200 may be configured to perform the BS behavioraccording to an implementation of the present disclosure or control thetransceiver(s) 206 to perform the BS behavior according to animplementation of the present disclosure.

In the present disclosure, a BS is also referred to as a node B (NB), aneNode B (eNB), or a gNB.

FIG. 3 shows an example of a wireless device to which implementations ofthe present disclosure is applied.

The wireless device may be implemented in various forms according to ause-case/service (refer to FIG. 1).

Referring to FIG. 3, wireless devices 100 and 200 may correspond to thewireless devices 100 and 200 of FIG. 2 and may be configured by variouselements, components, units/portions, and/or modules. For example, eachof the wireless devices 100 and 200 may include a communication unit110, a control unit 120, a memory unit 130, and additional components140. The communication unit 110 may include a communication circuit 112and transceiver(s) 114. For example, the communication circuit 112 mayinclude the one or more processors 102 and 202 of FIG. 2 and/or the oneor more memories 104 and 204 of FIG. 2. For example, the transceiver(s)114 may include the one or more transceivers 106 and 206 of FIG. 2and/or the one or more antennas 108 and 208 of FIG. 2. The control unit120 is electrically connected to the communication unit 110, the memory130, and the additional components 140 and controls overall operation ofeach of the wireless devices 100 and 200. For example, the control unit120 may control an electric/mechanical operation of each of the wirelessdevices 100 and 200 based on programs/code/commands/information storedin the memory unit 130. The control unit 120 may transmit theinformation stored in the memory unit 130 to the exterior (e.g., othercommunication devices) via the communication unit 110 through awireless/wired interface or store, in the memory unit 130, informationreceived through the wireless/wired interface from the exterior (e.g.,other communication devices) via the communication unit 110.

The additional components 140 may be variously configured according totypes of the wireless devices 100 and 200. For example, the additionalcomponents 140 may include at least one of a power unit/battery,input/output (I/O) unit (e.g., audio I/O port, video I/O port), adriving unit, and a computing unit. The wireless devices 100 and 200 maybe implemented in the form of, without being limited to, the robot (100a of FIG. 1), the vehicles (100 b-1 and 100 b-2 of FIG. 1), the XRdevice (100 c of FIG. 1), the hand-held device (100 d of FIG. 1), thehome appliance (100 e of FIG. 1), the IoT device (100 f of FIG. 1), adigital broadcast terminal, a hologram device, a public safety device,an MTC device, a medicine device, a FinTech device (or a financedevice), a security device, a climate/environment device, the AIserver/device (400 of FIG. 1), the BSs (200 of FIG. 1), a network node,etc. The wireless devices 100 and 200 may be used in a mobile or fixedplace according to a use-example/service.

In FIG. 3, the entirety of the various elements, components,units/portions, and/or modules in the wireless devices 100 and 200 maybe connected to each other through a wired interface or at least a partthereof may be wirelessly connected through the communication unit 110.For example, in each of the wireless devices 100 and 200, the controlunit 120 and the communication unit 110 may be connected by wire and thecontrol unit 120 and first units (e.g., 130 and 140) may be wirelesslyconnected through the communication unit 110. Each element, component,unit/portion, and/or module within the wireless devices 100 and 200 mayfurther include one or more elements. For example, the control unit 120may be configured by a set of one or more processors. As an example, thecontrol unit 120 may be configured by a set of a communication controlprocessor, an application processor (AP), an electronic control unit(ECU), a graphical processing unit, and a memory control processor. Asanother example, the memory 130 may be configured by a RAM, a DRAM, aROM, a flash memory, a volatile memory, a non-volatile memory, and/or acombination thereof.

FIG. 4 shows another example of wireless devices to whichimplementations of the present disclosure is applied.

Referring to FIG. 4, wireless devices 100 and 200 may correspond to thewireless devices 100 and 200 of FIG. 2 and may be configured by variouselements, components, units/portions, and/or modules.

The first wireless device 100 may include at least one transceiver, suchas a transceiver 106, and at least one processing chip, such as aprocessing chip 101. The processing chip 101 may include at least oneprocessor, such a processor 102, and at least one memory, such as amemory 104. The memory 104 may be operably connectable to the processor102. The memory 104 may store various types of information and/orinstructions. The memory 104 may store a software code 105 whichimplements instructions that, when executed by the processor 102,perform the descriptions, functions, procedures, suggestions, methodsand/or operational flowcharts disclosed in the present disclosure. Forexample, the software code 105 may implement instructions that, whenexecuted by the processor 102, perform the descriptions, functions,procedures, suggestions, methods and/or operational flowcharts disclosedin the present disclosure. For example, the software code 105 maycontrol the processor 102 to perform one or more protocols. For example,the software code 105 may control the processor 102 may perform one ormore layers of the radio interface protocol.

The second wireless device 200 may include at least one transceiver,such as a transceiver 206, and at least one processing chip, such as aprocessing chip 201. The processing chip 201 may include at least oneprocessor, such a processor 202, and at least one memory, such as amemory 204. The memory 204 may be operably connectable to the processor202. The memory 204 may store various types of information and/orinstructions. The memory 204 may store a software code 205 whichimplements instructions that, when executed by the processor 202,perform the descriptions, functions, procedures, suggestions, methodsand/or operational flowcharts disclosed in the present disclosure. Forexample, the software code 205 may implement instructions that, whenexecuted by the processor 202, perform the descriptions, functions,procedures, suggestions, methods and/or operational flowcharts disclosedin the present disclosure. For example, the software code 205 maycontrol the processor 202 to perform one or more protocols. For example,the software code 205 may control the processor 202 may perform one ormore layers of the radio interface protocol.

FIG. 5 shows an example of UE to which implementations of the presentdisclosure is applied.

Referring to FIG. 5, a UE 100 may correspond to the first wirelessdevice 100 of FIG. 2 and/or the first wireless device 100 of FIG. 4.

A UE 100 includes a processor 102, a memory 104, a transceiver 106, oneor more antennas 108, a power management module 110, a battery 1112, adisplay 114, a keypad 116, a subscriber identification module (SIM) card118, a speaker 120, and a microphone 122.

The processor 102 may be configured to implement the descriptions,functions, procedures, suggestions, methods and/or operationalflowcharts disclosed in the present disclosure. The processor 102 may beconfigured to control one or more other components of the UE 100 toimplement the descriptions, functions, procedures, suggestions, methodsand/or operational flowcharts disclosed in the present disclosure.Layers of the radio interface protocol may be implemented in theprocessor 102. The processor 102 may include ASIC, other chipset, logiccircuit and/or data processing device. The processor 102 may be anapplication processor. The processor 102 may include at least one of adigital signal processor (DSP), a central processing unit (CPU), agraphics processing unit (GPU), a modem (modulator and demodulator). Anexample of the processor 102 may be found in SNAPDRAGON™ series ofprocessors made by Qualcomm®, EXYNOS™ series of processors made bySamsung®, A series of processors made by Apple®, HELIO™ series ofprocessors made by MediaTek®, ATOM™ series of processors made by Intel®or a corresponding next generation processor.

The memory 104 is operatively coupled with the processor 102 and storesa variety of information to operate the processor 102. The memory 104may include ROM, RAM, flash memory, memory card, storage medium and/orother storage device. When the embodiments are implemented in software,the techniques described herein can be implemented with modules (e.g.,procedures, functions, etc.) that perform the descriptions, functions,procedures, suggestions, methods and/or operational flowcharts disclosedin the present disclosure. The modules can be stored in the memory 104and executed by the processor 102. The memory 104 can be implementedwithin the processor 102 or external to the processor 102 in which casethose can be communicatively coupled to the processor 102 via variousmeans as is known in the art.

The transceiver 106 is operatively coupled with the processor 102, andtransmits and/or receives a radio signal. The transceiver 106 includes atransmitter and a receiver. The transceiver 106 may include basebandcircuitry to process radio frequency signals. The transceiver 106controls the one or more antennas 108 to transmit and/or receive a radiosignal.

The power management module 110 manages power for the processor 102and/or the transceiver 106. The battery 112 supplies power to the powermanagement module 110.

The display 114 outputs results processed by the processor 102. Thekeypad 116 receives inputs to be used by the processor 102. The keypad16 may be shown on the display 114.

The SIM card 118 is an integrated circuit that is intended to securelystore the international mobile subscriber identity (IMSI) number and itsrelated key, which are used to identify and authenticate subscribers onmobile telephony devices (such as mobile phones and computers). It isalso possible to store contact information on many SIM cards.

The speaker 120 outputs sound-related results processed by the processor102. The microphone 122 receives sound-related inputs to be used by theprocessor 102.

Hereinafter, an apparatus for conditional handover based on the servicetime of candidate cells in a wireless communication system, according tosome embodiments of the present disclosure, will be described.

Referring to FIG. 5, a wireless device 100 may include a processor 102,a memory 104, and a transceiver 106.

According to some embodiments of the present disclosure, the processor102 may be configured to be coupled operably with the memory 104 and thetransceiver 106.

The processor 102 may be configured to control the transceiver 106 toreceive, from a network, handover configuration including informationrelated to candidate cells to be measured and service time of each ofthe candidate cells. The processor 102 may be configured to performmeasurement on the candidate cells. The processor 102 may be configuredto select a cell among the candidate cells based on the service time ofeach of the candidate cells. The processor 102 may be configured toperform handover to the selected cell.

According to some embodiments of the present disclosure, the processor106 may be further configured to determine whether each of the candidatecells is met a handover condition. For example, the handoverconfiguration may include information on the handover condition. Forexample, the cell may be selected among the candidate cells which aremet the handover condition.

According to some embodiments of the present disclosure, the processor106 may be configured to select a cell among the candidate cells basedon remaining time of the service time of each of the candidate cellsfrom a specific time point. In other words, the cell is selected amongthe candidate cells based on remaining time of the service time of eachof the candidate cells from a specific time point. For example, themeasurement on the candidate cells may be performed at the specificpoint.

Hereinafter, a processor for a wireless device for conditional handoverbased on the service time of candidate cells in a wireless communicationsystem, according to some embodiments of the present disclosure, will bedescribed.

The processor may be configured to control the wireless device toreceive, from a network, handover configuration including informationrelated to candidate cells to be measured and service time of each ofthe candidate cells. The processor may be configured to control thewireless device to perform measurement on the candidate cells. Theprocessor may be configured to control the wireless device to select acell among the candidate cells based on the service time of each of thecandidate cells. The processor may be configured to control the wirelessdevice to perform handover to the selected cell.

Hereinafter, a non-transitory computer-readable medium which has storedthereon a plurality of instructions for conditional handover based onthe service time of candidate cells in a wireless communication system,according to some embodiments of the present disclosure, will bedescribed.

According to some embodiment of the present disclosure, the technicalfeatures of the present disclosure could be embodied directly inhardware, in a software executed by a processor, or in a combination ofthe two. For example, a method performed by a wireless device in awireless communication may be implemented in hardware, software,firmware, or any combination thereof. For example, a software may residein RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory,registers, hard disk, a removable disk, a CD-ROM, or any other storagemedium.

Some example of storage medium is coupled to the processor such that theprocessor can read information from the storage medium. In thealternative, the storage medium may be integral to the processor. Theprocessor and the storage medium may reside in an ASIC. For otherexample, the processor and the storage medium may reside as discretecomponents.

The computer-readable medium may include a tangible and non-transitorycomputer-readable storage medium.

For example, non-transitory computer-readable media may include randomaccess memory (RAM) such as synchronous dynamic random access memory(SDRAM), read-only memory (ROM), non-volatile random access memory(NVRAM), electrically erasable programmable read-only memory (EEPROM),FLASH memory, magnetic or optical data storage media, or any othermedium that can be used to store instructions or data structures.Non-transitory computer-readable media may also include combinations ofthe above.

In addition, the method described herein may be realized at least inpart by a computer-readable communication medium that carries orcommunicates code in the form of instructions or data structures andthat can be accessed, read, and/or executed by a computer.

According to some embodiment of the present disclosure, a non-transitorycomputer-readable medium has stored thereon a plurality of instructions.The stored a plurality of instructions may be executed by a processor ofa wireless device.

The stored a plurality of instructions may cause the wireless device toreceive, from a network, handover configuration including informationrelated to candidate cells to be measured and service time of each ofthe candidate cells. The stored a plurality of instructions may causethe wireless device to perform measurement on the candidate cells. Thestored a plurality of instructions may cause the wireless device toselect a cell among the candidate cells based on the service time ofeach of the candidate cells. The stored a plurality of instructions maycause the wireless device to perform handover to the selected cell.

FIGS. 6 and 7 show an example of protocol stacks in a 3GPP basedwireless communication system to which implementations of the presentdisclosure is applied.

In particular, FIG. 6 illustrates an example of a radio interface userplane protocol stack between a UE and a BS and FIG. 7 illustrates anexample of a radio interface control plane protocol stack between a UEand a BS. The control plane refers to a path through which controlmessages used to manage call by a UE and a network are transported. Theuser plane refers to a path through which data generated in anapplication layer, for example, voice data or Internet packet data aretransported. Referring to FIG. 6, the user plane protocol stack may bedivided into Layer 1 (i.e., a PHY layer) and Layer 2. Referring to FIG.7, the control plane protocol stack may be divided into Layer 1 (i.e., aPHY layer), Layer 2, Layer 3 (e.g., an RRC layer), and a non-accessstratum (NAS) layer. Layer 1, Layer 2 and Layer 3 are referred to as anaccess stratum (AS).

In the 3GPP LTE system, the Layer 2 is split into the followingsublayers: MAC, RLC, and PDCP. In the 3GPP NR system, the Layer 2 issplit into the following sublayers: MAC, RLC, PDCP and SDAP. The PHYlayer offers to the MAC sublayer transport channels, the MAC sublayeroffers to the RLC sublayer logical channels, the RLC sublayer offers tothe PDCP sublayer RLC channels, the PDCP sublayer offers to the SDAPsublayer radio bearers. The SDAP sublayer offers to 5G core networkquality of service (QoS) flows.

In the 3GPP NR system, the main services and functions of the MACsublayer include: mapping between logical channels and transportchannels; multiplexing/de-multiplexing of MAC SDUs belonging to one ordifferent logical channels into/from transport blocks (TB) deliveredto/from the physical layer on transport channels; scheduling informationreporting; error correction through hybrid automatic repeat request(HARQ) (one HARQ entity per cell in case of carrier aggregation (CA));priority handling between UEs by means of dynamic scheduling; priorityhandling between logical channels of one UE by means of logical channelprioritization; padding. A single MAC entity may support multiplenumerologies, transmission timings and cells. Mapping restrictions inlogical channel prioritization control which numerology(ies), cell(s),and transmission timing(s) a logical channel can use.

Different kinds of data transfer services are offered by MAC. Toaccommodate different kinds of data transfer services, multiple types oflogical channels are defined, i.e., each supporting transfer of aparticular type of information. Each logical channel type is defined bywhat type of information is transferred. Logical channels are classifiedinto two groups: control channels and traffic channels. Control channelsare used for the transfer of control plane information only, and trafficchannels are used for the transfer of user plane information only.Broadcast control channel (BCCH) is a downlink logical channel forbroadcasting system control information, paging control channel (PCCH)is a downlink logical channel that transfers paging information, systeminformation change notifications and indications of ongoing publicwarning service (PWS) broadcasts, common control channel (CCCH) is alogical channel for transmitting control information between UEs andnetwork and used for UEs having no RRC connection with the network, anddedicated control channel (DCCH) is a point-to-point bi-directionallogical channel that transmits dedicated control information between aUE and the network and used by UEs having an RRC connection. Dedicatedtraffic channel (DTCH) is a point-to-point logical channel, dedicated toone UE, for the transfer of user information. A DTCH can exist in bothuplink and downlink. In downlink, the following connections betweenlogical channels and transport channels exist: BCCH can be mapped tobroadcast channel (BCH); BCCH can be mapped to downlink shared channel(DL-SCH); PCCH can be mapped to paging channel (PCH); CCCH can be mappedto DL-SCH; DCCH can be mapped to DL-SCH; and DTCH can be mapped toDL-SCH. In uplink, the following connections between logical channelsand transport channels exist: CCCH can be mapped to uplink sharedchannel (UL-SCH); DCCH can be mapped to UL-SCH; and DTCH can be mappedto UL-SCH.

The RLC sublayer supports three transmission modes: transparent mode(TM), unacknowledged mode (UM), and acknowledged node (AM). The RLCconfiguration is per logical channel with no dependency on numerologiesand/or transmission durations. In the 3GPP NR system, the main servicesand functions of the RLC sublayer depend on the transmission mode andinclude: transfer of upper layer PDUs; sequence numbering independent ofthe one in PDCP (UM and AM); error correction through ARQ (AM only);segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs;reassembly of SDU (AM and UM); duplicate detection (AM only); RLC SDUdiscard (AM and UM); RLC re-establishment; protocol error detection (AMonly).

In the 3GPP NR system, the main services and functions of the PDCPsublayer for the user plane include: sequence numbering; headercompression and decompression using robust header compression (ROHC);transfer of user data; reordering and duplicate detection; in-orderdelivery; PDCP PDU routing (in case of split bearers); retransmission ofPDCP SDUs; ciphering, deciphering and integrity protection; PDCP SDUdiscard; PDCP re-establishment and data recovery for RLC AM; PDCP statusreporting for RLC AM; duplication of PDCP PDUs and duplicate discardindication to lower layers. The main services and functions of the PDCPsublayer for the control plane include: sequence numbering; ciphering,deciphering and integrity protection; transfer of control plane data;reordering and duplicate detection; in-order delivery; duplication ofPDCP PDUs and duplicate discard indication to lower layers.

In the 3GPP NR system, the main services and functions of SDAP include:mapping between a QoS flow and a data radio bearer; marking QoS flow ID(QFI) in both DL and UL packets. A single protocol entity of SDAP isconfigured for each individual PDU session.

In the 3GPP NR system, the main services and functions of the RRCsublayer include: broadcast of system information related to AS and NAS;paging initiated by 5GC or NG-RAN; establishment, maintenance andrelease of an RRC connection between the UE and NG-RAN; securityfunctions including key management; establishment, configuration,maintenance and release of signaling radio bearers (SRBs) and data radiobearers (DRBs); mobility functions (including: handover and contexttransfer, UE cell selection and reselection and control of cellselection and reselection, inter-RAT mobility); QoS managementfunctions; UE measurement reporting and control of the reporting;detection of and recovery from radio link failure; NAS message transferto/from NAS from/to UE.

FIG. 8 shows a frame structure in a 3GPP based wireless communicationsystem to which implementations of the present disclosure is applied.

The frame structure shown in FIG. 8 is purely exemplary and the numberof subframes, the number of slots, and/or the number of symbols in aframe may be variously changed. In the 3GPP based wireless communicationsystem, OFDM numerologies (e.g., subcarrier spacing (SCS), transmissiontime interval (TTI) duration) may be differently configured between aplurality of cells aggregated for one UE. For example, if a UE isconfigured with different SCSs for cells aggregated for the cell, an(absolute time) duration of a time resource (e.g., a subframe, a slot,or a TTI) including the same number of symbols may be different amongthe aggregated cells. Herein, symbols may include OFDM symbols (orCP-OFDM symbols), SC-FDMA symbols (or discrete Fouriertransform-spread-OFDM (DFT-s-OFDM) symbols).

Referring to FIG. 8, downlink and uplink transmissions are organizedinto frames. Each frame has T_(f)=10 ms duration. Each frame is dividedinto two half-frames, where each of the half-frames has 5 ms duration.Each half-frame consists of 5 subframes, where the duration T_(sf) persubframe is 1 ms. Each subframe is divided into slots and the number ofslots in a subframe depends on a subcarrier spacing. Each slot includes14 or 12 OFDM symbols based on a cyclic prefix (CP). In a normal CP,each slot includes 14 OFDM symbols and, in an extended CP, each slotincludes 12 OFDM symbols. The numerology is based on exponentiallyscalable subcarrier spacing Δf=2^(u)*15 kHz.

Table 1 shows the number of OFDM symbols per slot N^(slot) _(symb), thenumber of slots per frame N^(frame,u) _(slot), and the number of slotsper subframe N^(subframe,u) _(slot) for the normal CP, according to thesubcarrier spacing Δf=2^(u)*15 kHz.

TABLE 1 u N^(slot) _(symb) N^(frame,u) _(slot) N^(subframe,u) _(slot) 014 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16

Table 2 shows the number of OFDM symbols per slot N^(slot) _(symb), thenumber of slots per frame N^(frame,u) _(slot), and the number of slotsper subframe N^(subframe,u) _(slot) for the extended CP, according tothe subcarrier spacing Δf=2^(u)*15 kHz.

TABLE 2 u N^(slot) _(symb) N^(frame,u) _(slot) N^(subframe,u) _(slot) 212 40 4

A slot includes plural symbols (e.g., 14 or 12 symbols) in the timedomain. For each numerology (e.g., subcarrier spacing) and carrier, aresource grid of N^(size,u) _(grid,x)*N^(RB) _(sc) subcarriers andN^(subframe,u) _(symb) OFDM symbols is defined, starting at commonresource block (CRB) N^(start,u) _(grid) indicated by higher-layersignaling (e.g., RRC signaling), where N^(size,u) _(grid,x) is thenumber of resource blocks (RBs) in the resource grid and the subscript xis DL for downlink and UL for uplink. N^(RB) _(sc) is the number ofsubcarriers per RB. In the 3GPP based wireless communication system,N^(RB) _(sc) is 12 generally. There is one resource grid for a givenantenna port p, subcarrier spacing configuration u, and transmissiondirection (DL or UL). The carrier bandwidth N^(size,u) _(grid) forsubcarrier spacing configuration u is given by the higher-layerparameter (e.g., RRC parameter). Each element in the resource grid forthe antenna port p and the subcarrier spacing configuration u isreferred to as a resource element (RE) and one complex symbol may bemapped to each RE. Each RE in the resource grid is uniquely identifiedby an index kin the frequency domain and an index l representing asymbol location relative to a reference point in the time domain. In the3GPP based wireless communication system, an RB is defined by 12consecutive subcarriers in the frequency domain. In the 3GPP NR system,RBs are classified into CRBs and physical resource blocks (PRBs). CRBsare numbered from 0 and upwards in the frequency domain for subcarrierspacing configuration u. The center of subcarrier 0 of CRB 0 forsubcarrier spacing configuration u coincides with ‘point A’ which servesas a common reference point for resource block grids. In the 3GPP NRsystem, PRBs are defined within a bandwidth part (BWP) and numbered from0 to N^(size) _(BWP,i)−1, where i is the number of the bandwidth part.The relation between the physical resource block n_(PRB) in thebandwidth part i and the common resource block n_(CRB) is as follows:n_(PRB)=n_(CRB)+N^(size) _(BWP,i), where N^(size) _(BWP,i) is the commonresource block where bandwidth part starts relative to CRB 0. The BWPincludes a plurality of consecutive RBs. A carrier may include a maximumof N (e.g., 5) BWPs. A UE may be configured with one or more BWPs on agiven component carrier. Only one BWP among BWPs configured to the UEcan active at a time. The active BWP defines the UE's operatingbandwidth within the cell's operating bandwidth.

The NR frequency band may be defined as two types of frequency range,i.e., FR1 and FR2. The numerical value of the frequency range may bechanged. For example, the frequency ranges of the two types (FR1 andFR2) may be as shown in Table 3 below. For ease of explanation, in thefrequency ranges used in the NR system, FR1 may mean “sub 6 GHz range”,FR2 may mean “above 6 GHz range,” and may be referred to as millimeterwave (mmW).

TABLE 3 Frequency Range Corresponding Subcarrier designation frequencyrange Spacing FR1  450 MHz-6000 MHz 15, 30, 60 kHz FR2 24250 MHz-52600MHz 60, 120, 240 kHz

As mentioned above, the numerical value of the frequency range of the NRsystem may be changed. For example, FR1 may include a frequency band of410 MHz to 7125 MHz as shown in Table 4 below. That is, FR1 may includea frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or more. Forexample, a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) ormore included in FR1 may include an unlicensed band. Unlicensed bandsmay be used for a variety of purposes, for example for communication forvehicles (e.g., autonomous driving).

TABLE 4 Frequency Range Corresponding Subcarrier designation frequencyrange Spacing FR1  410 MHz-7125 MHz 15, 30, 60 kHz FR2 24250 MHz-52600MHz 60, 120, 240 kHz

In the present disclosure, the term “cell” may refer to a geographicarea to which one or more nodes provide a communication system, or referto radio resources. A “cell” as a geographic area may be understood ascoverage within which a node can provide service using a carrier and a“cell” as radio resources (e.g., time-frequency resources) is associatedwith bandwidth which is a frequency range configured by the carrier. The“cell” associated with the radio resources is defined by a combinationof downlink resources and uplink resources, for example, a combinationof a DL component carrier (CC) and a UL CC. The cell may be configuredby downlink resources only, or may be configured by downlink resourcesand uplink resources. Since DL coverage, which is a range within whichthe node is capable of transmitting a valid signal, and UL coverage,which is a range within which the node is capable of receiving the validsignal from the UE, depends upon a carrier carrying the signal, thecoverage of the node may be associated with coverage of the “cell” ofradio resources used by the node. Accordingly, the term “cell” may beused to represent service coverage of the node sometimes, radioresources at other times, or a range that signals using the radioresources can reach with valid strength at other times. In CA, two ormore CCs are aggregated. A UE may simultaneously receive or transmit onone or multiple CCs depending on its capabilities. CA is supported forboth contiguous and non-contiguous CCs. When CA is configured, the UEonly has one RRC connection with the network. At RRC connectionestablishment/re-establishment/handover, one serving cell provides theNAS mobility information, and at RRC connectionre-establishment/handover, one serving cell provides the security input.This cell is referred to as the primary cell (PCell). The PCell is acell, operating on the primary frequency, in which the UE eitherperforms the initial connection establishment procedure or initiates theconnection re-establishment procedure. Depending on UE capabilities,secondary cells (SCells) can be configured to form together with thePCell a set of serving cells. An SCell is a cell providing additionalradio resources on top of special cell (SpCell). The configured set ofserving cells for a UE therefore always consists of one PCell and one ormore SCells. For dual connectivity (DC) operation, the term SpCellrefers to the PCell of the master cell group (MCG) or the primary SCell(PSCell) of the secondary cell group (SCG). An SpCell supports PUCCHtransmission and contention-based random access, and is alwaysactivated. The MCG is a group of serving cells associated with a masternode, comprised of the SpCell (PCell) and optionally one or more SCells.The SCG is the subset of serving cells associated with a secondary node,comprised of the PSCell and zero or more SCells, for a UE configuredwith DC. For a UE in RRC_CONNECTED not configured with CA/DC, there isonly one serving cell comprised of the PCell. For a UE in RRC_CONNECTEDconfigured with CA/DC, the term “serving cells” is used to denote theset of cells comprised of the SpCell(s) and all SCells. In DC, two MACentities are configured in a UE: one for the MCG and one for the SCG.

FIG. 9 shows a data flow example in the 3GPP NR system to whichimplementations of the present disclosure is applied.

Referring to FIG. 9, “RB” denotes a radio bearer, and “H” denotes aheader. Radio bearers are categorized into two groups: DRBs for userplane data and SRBs for control plane data. The MAC PDU istransmitted/received using radio resources through the PHY layer to/froman external device. The MAC PDU arrives to the PHY layer in the form ofa transport block.

In the PHY layer, the uplink transport channels UL-SCH and RACH aremapped to their physical channels PUSCH and PRACH, respectively, and thedownlink transport channels DL-SCH, BCH and PCH are mapped to PDSCH,PBCH and PDSCH, respectively. In the PHY layer, uplink controlinformation (UCI) is mapped to PUCCH, and downlink control information(DCI) is mapped to PDCCH. A MAC PDU related to UL-SCH is transmitted bya UE via a PUSCH based on an UL grant, and a MAC PDU related to DL-SCHis transmitted by a BS via a PDSCH based on a DL assignment.

In order to transmit data unit(s) of the present disclosure on UL-SCH, aUE shall have uplink resources available to the UE. In order to receivedata unit(s) of the present disclosure on DL-SCH, a UE shall havedownlink resources available to the UE. The resource allocation includestime domain resource allocation and frequency domain resourceallocation. In the present disclosure, uplink resource allocation isalso referred to as uplink grant, and downlink resource allocation isalso referred to as downlink assignment. An uplink grant is eitherreceived by the UE dynamically on PDCCH, in a random access response, orconfigured to the UE semi-persistently by RRC. Downlink assignment iseither received by the UE dynamically on the PDCCH, or configured to theUE semi-persistently by RRC signaling from the BS.

In UL, the BS can dynamically allocate resources to UEs via the cellradio network temporary identifier (C-RNTI) on PDCCH(s). A UE alwaysmonitors the PDCCH(s) in order to find possible grants for uplinktransmission when its downlink reception is enabled (activity governedby discontinuous reception (DRX) when configured). In addition, withconfigured grants, the BS can allocate uplink resources for the initialHARQ transmissions to UEs. Two types of configured uplink grants aredefined: Type 1 and Type 2. With Type 1, RRC directly provides theconfigured uplink grant (including the periodicity). With Type 2, RRCdefines the periodicity of the configured uplink grant while PDCCHaddressed to configured scheduling RNTI (CS-RNTI) can either signal andactivate the configured uplink grant, or deactivate it. That is, a PDCCHaddressed to CS-RNTI indicates that the uplink grant can be implicitlyreused according to the periodicity defined by RRC, until deactivated.

In DL, the BS can dynamically allocate resources to UEs via the C-RNTIon PDCCH(s). A UE always monitors the PDCCH(s) in order to find possibleassignments when its downlink reception is enabled (activity governed byDRX when configured). In addition, with semi-persistent Scheduling(SPS), the BS can allocate downlink resources for the initial HARQtransmissions to UEs. RRC defines the periodicity of the configureddownlink assignments while PDCCH addressed to CS-RNTI can either signaland activate the configured downlink assignment, or deactivate it. Inother words, a PDCCH addressed to CS-RNTI indicates that the downlinkassignment can be implicitly reused according to the periodicity definedby RRC, until deactivated.

For resource allocation by PDCCH (i.e., resource allocation by DCI),PDCCH can be used to schedule DL transmissions on PDSCH and ULtransmissions on PUSCH, where the DCI on PDCCH includes: downlinkassignments containing at least modulation and coding format (e.g.,modulation and coding scheme (MCS) index I_(MCS)), resource allocation,and hybrid-ARQ information related to DL-SCH; or uplink schedulinggrants containing at least modulation and coding format, resourceallocation, and hybrid-ARQ information related to UL-SCH. The size andusage of the DCI carried by one PDCCH are varied depending on DCIformats. For example, in the 3GPP NR system, DCI format 0_0 or DCIformat 0_1 is used for scheduling of PUSCH in one cell, and DCI format1_0 or DCI format 1_1 is used for scheduling of PDSCH in one cell.

Hereinafter, events for measurement report triggering will be described.It may be referred to as Section 5.5.4 of 3GPP TS 38.331 v15.5.1.

Event A1 (Serving becomes better than threshold) is described.

The UE shall:

1> consider the entering condition for this event to be satisfied whencondition A1-1, as specified below, is fulfilled;

1> consider the leaving condition for this event to be satisfied whencondition A1-2, as specified below, is fulfilled;

1> for this measurement, consider the NR serving cell corresponding tothe associated measObjectNR associated with this event.

Ms−Hys>Thresh  Inequality A1-1 (Entering condition)

Ms+Hys<Thresh  Inequality A1-2 (Leaving condition)

The variables in the formula are defined as follows:

Ms is the measurement result of the serving cell, not taking intoaccount any offsets.

Hys is the hysteresis parameter for this event (i.e. hysteresis asdefined within reportConfigNR for this event).

Thresh is the threshold parameter for this event (i.e. a1-Threshold asdefined within reportConfigNR for this event).

Ms is expressed in dBm in case of RSRP, or in dB in case of RSRQ andRS-SINR.

Hys is expressed in dB.

Thresh is expressed in the same unit as Ms.

Event A2 (Serving becomes worse than threshold) is described.

The UE shall:

1> consider the entering condition for this event to be satisfied whencondition A2-1, as specified below, is fulfilled;

1> consider the leaving condition for this event to be satisfied whencondition A2-2, as specified below, is fulfilled;

1> for this measurement, consider the serving cell indicated by themeasObjectNR associated to this event.

Ms+Hys<Thresh  Inequality A2-1 (Entering condition)

Ms−Hys>Thresh  Inequality A2-2 (Leaving condition)

The variables in the formula are defined as follows:

Ms is the measurement result of the serving cell, not taking intoaccount any offsets.

Hys is the hysteresis parameter for this event (i.e. hysteresis asdefined within reportConfigNR for this event).

Thresh is the threshold parameter for this event (i.e. a2-Threshold asdefined within reportConfigNR for this event).

Ms is expressed in dBm in case of RSRP, or in dB in case of RSRQ andRS-SINR.

Hys is expressed in dB.

Thresh is expressed in the same unit as Ms.

Event A3 (Neighbour becomes offset better than SpCell) is described.

The UE shall:

1> consider the entering condition for this event to be satisfied whencondition A3-1, as specified below, is fulfilled;

1> consider the leaving condition for this event to be satisfied whencondition A3-2, as specified below, is fulfilled;

1> use the SpCell for Mp, Ofp and Ocp.

The cell(s) that triggers the event has reference signals indicated inthe measObjectNR associated to this event which may be different fromthe NR SpCell measObjectNR.

Mn+Ofn+Ocn−Hys>Mp+Ofp+Ocp+Off  Inequality A3-1 (Entering condition)

Mn+Ofn+Ocn+Hys<Mp+Ofp+Ocp+Off  Inequality A3-2 (Leaving condition)

The variables in the formula are defined as follows:

Mn is the measurement result of the neighbouring cell, not taking intoaccount any offsets.

Ofn is the measurement object specific offset of the reference signal ofthe neighbour cell (i.e. offsetMO as defined within measObjectNRcorresponding to the neighbour cell).

Ocn is the cell specific offset of the neighbour cell (i.e.celllndividualOffset as defined within measObjectNR corresponding to thefrequency of the neighbour cell), and set to zero if not configured forthe neighbour cell.

Mp is the measurement result of the SpCell, not taking into account anyoffsets.

Ofp is the measurement object specific offset of the SpCell (i.e.offsetMO as defined within measObjectNR corresponding to the SpCell).

Ocp is the cell specific offset of the SpCell (i.e. celllndividualOffsetas defined within measObjectNR corresponding to the SpCell), and is setto zero if not configured for the SpCell.

Hys is the hysteresis parameter for this event (i.e. hysteresis asdefined within reportConfigNR for this event).

Off is the offset parameter for this event (i.e. a3-Offset as definedwithin reportConfigNR for this event).

Mn, Mp are expressed in dBm in case of RSRP, or in dB in case of RSRQand RS-SINR.

Ofn, Ocn, Ofp, Ocp, Hys, Off are expressed in dB.

Event A4 (Neighbour becomes better than threshold) is described.

The UE shall:

1> consider the entering condition for this event to be satisfied whencondition A4-1, as specified below, is fulfilled;

1> consider the leaving condition for this event to be satisfied whencondition A4-2, as specified below, is fulfilled.

Mn+Ofn+Ocn−Hys>Thresh  Inequality A4-1 (Entering condition)

Mn+Ofn+Ocn+Hys<Thresh  Inequality A4-2 (Leaving condition)

The variables in the formula are defined as follows:

Mn is the measurement result of the neighbouring cell, not taking intoaccount any offsets.

Ofn is the measurement object specific offset of the neighbour cell(i.e. offsetMO as defined within measObjectNR corresponding to theneighbour cell).

Ocn is the measurement object specific offset of the neighbour cell(i.e. celllndividualOffset as defined within measObjectNR correspondingto the neighbour cell), and set to zero if not configured for theneighbour cell.

Hys is the hysteresis parameter for this event (i.e. hysteresis asdefined within reportConfigNR for this event).

Thresh is the threshold parameter for this event (i.e. a4-Threshold asdefined within reportConfigNR for this event).

Mn is expressed in dBm in case of RSRP, or in dB in case of RSRQ andRS-SINR.

Ofn, Ocn, Hys are expressed in dB.

Thresh is expressed in the same unit as Mn.

Event A5 (SpCell becomes worse than threshold) and neighbour becomesbetter than threshold2) is described.

The UE shall:

1> consider the entering condition for this event to be satisfied whenboth condition A5-1 and condition A5-2, as specified below, arefulfilled;

1> consider the leaving condition for this event to be satisfied whencondition A5-3 or condition A5-4, i.e. at least one of the two, asspecified below, is fulfilled;

1> use the SpCell for Mp.

The parameters of the reference signal(s) of the cell(s) that triggersthe event are indicated in the measObjectNR associated to the eventwhich may be different from the measObjectNR of the NR SpCell.

Mp+Hys<Thresh1  Inequality A5-1 (Entering condition 1)

Mn+Ofn+Ocn−Hys>Thresh2  Inequality A5-2 (Entering condition 2)

Mp−Hys>Thresh1  Inequality A5-3 (Leaving condition 1)

Mn+Ofn+Ocn+Hys<Thresh2  Inequality A5-4 (Leaving condition 2)

The variables in the formula are defined as follows:

Mp is the measurement result of the NR SpCell, not taking into accountany offsets.

Mn is the measurement result of the neighbouring cell, not taking intoaccount any offsets.

Ofn is the measurement object specific offset of the neighbour cell(i.e. offsetMO as defined within measObjectNR corresponding to theneighbour cell).

Ocn is the cell specific offset of the neighbour cell (i.e.celllndividualOffset as defined within measObjectNR corresponding to theneighbour cell), and set to zero if not configured for the neighbourcell.

Hys is the hysteresis parameter for this event (i.e. hysteresis asdefined within reportConfigNR for this event).

Thresh1 is the threshold parameter for this event (i.e. a5-Threshold1 asdefined within reportConfigNR for this event).

Thresh2 is the threshold parameter for this event (i.e. a5-Threshold2 asdefined within reportConfigNR for this event).

Mn, Mp are expressed in dBm in case of RSRP, or in dB in case of RSRQand RS-SINR.

Ofn, Ocn, Hys are expressed in dB.

Thresh1 is expressed in the same unit as Mp.

Thresh2 is expressed in the same unit as Mn.

Event A6 (Neighbour becomes offset better than SCell) is described.

The UE shall:

1> consider the entering condition for this event to be satisfied whencondition A6-1, as specified below, is fulfilled;

1> consider the leaving condition for this event to be satisfied whencondition A6-2, as specified below, is fulfilled;

1> for this measurement, consider the (secondary) cell corresponding tothe measObjectNR associated to this event to be the serving cell.

The reference signal(s) of the neighbour(s) and the reference signal(s)of the SCell are both indicated in the associated measObjectNR.

Mn+Ocn−Hys>Ms+Ocs+Off  Inequality A6-1 (Entering condition)

Mn+Ocn+Hys<Ms+Ocs+Off  Inequality A6-2 (Leaving condition)

The variables in the formula are defined as follows:

Mn is the measurement result of the neighbouring cell, not taking intoaccount any offsets.

Ocn is the cell specific offset of the neighbour cell (i.e.celllndividualOffset as defined within the associated measObjectNR), andset to zero if not configured for the neighbour cell.

Ms is the measurement result of the serving cell, not taking intoaccount any offsets.

Ocs is the cell specific offset of the serving cell (i.e.celllndividualOffset as defined within the associated measObjectNR), andis set to zero if not configured for the serving cell.

Hys is the hysteresis parameter for this event (i.e. hysteresis asdefined within reportConfigNR for this event).

Off is the offset parameter for this event (i.e. a6-Offset as definedwithin reportConfigNR for this event).

Mn, Ms are expressed in dBm in case of RSRP, or in dB in case of RSRQand RS-SINR.

Ocn, Ocs, Hys, Off are expressed in dB.

Hereinafter, handover procedure is described. It may be referred to asSection 9.2.3.2 of 3GPP TS 38.300 v15.5.0.

C-Plane handling is described. The intra-NR RAN handover performs thepreparation and execution phase of the handover procedure performedwithout involvement of the 5GC. For example, preparation messages aredirectly exchanged between the gNBs. The release of the resources at thesource gNB during the handover completion phase is triggered by thetarget gNB. The basic handover scenario where neither the AMF nor theUPF changes is as follow.

0. The UE context within the source gNB contains information regardingroaming and access restrictions which were provided either at connectionestablishment or at the last TA update.

1. The source gNB configures the UE measurement procedures and the UEreports according to the measurement configuration.

2. The source gNB decides to handover the UE, based on MeasurementReportand RRM information.

3. The source gNB issues a Handover Request message to the target gNBpassing a transparent RRC container with necessary information toprepare the handover at the target side. The information includes atleast the target cell ID, KgNB*, the C-RNTI of the UE in the source gNB,RRM-configuration including UE inactive time, basic AS-configurationincluding antenna Info and DL Carrier Frequency, the current QoS flow toDRB mapping rules applied to the UE, the SIB1 from source gNB, the UEcapabilities for different RATs, PDU session related information, andcan include the UE reported measurement information includingbeam-related information if available. The PDU session relatedinformation includes the slice information (if supported) and QoS flowlevel QoS profile(s).

After issuing a Handover Request, the source gNB should not reconfigurethe UE, including performing Reflective QoS flow to DRB mapping.

4. Admission Control may be performed by the target gNB. Slice-awareadmission control shall be performed if the slice information is sent tothe target gNB. If the PDU sessions are associated with non-supportedslices the target gNB shall reject such PDU Sessions.

5. The target gNB prepares the handover with L1/L2 and sends theHANDOVER

REQUEST ACKNOWLEDGE to the source gNB, which includes a transparentcontainer to be sent to the UE as an RRC message to perform thehandover.

6. The source gNB triggers the Uu handover by sending anRRCReconfiguration message to the UE, containing the informationrequired to access the target cell: at least the target cell ID, the newC-RNTI, the target gNB security algorithm identifiers for the selectedsecurity algorithms. It can also include a set of dedicated RACHresources, the association between RACH resources and SSB(s), theassociation between RACH resources and UE-specific CSI-RSconfiguration(s), common RACH resources, and system information of thetarget cell, etc.

7. The source gNB sends the SN STATUS TRANSFER message to the targetgNB.

8. The UE synchronises to the target cell and completes the RRC handoverprocedure by sending RRCReconfigurationComplete message to target gNB.

9. The target gNB sends a PATH SWITCH REQUEST message to AMF to trigger5GC to switch the DL data path towards the target gNB and to establishan NG-C interface instance towards the target gNB.

10. 5GC switches the DL data path towards the target gNB. The UPF sendsone or more “end marker” packets on the old path to the source gNB perPDU session/tunnel and then can release any U-plane/TNL resourcestowards the source gNB.

11. The AMF confirms the PATH SWITCH REQUEST message with the PATHSWITCH REQUEST ACKNOWLEDGE message.

12. Upon reception of the PATH SWITCH REQUEST ACKNOWLEDGE message fromthe AMF, the target gNB sends the UE CONTEXT RELEASE to inform thesource gNB about the success of the handover. The source gNB can thenrelease radio and C-plane related resources associated to the UEcontext. Any ongoing data forwarding may continue.

Non-terrestrial networks (NTN) in 5G NR is described. Section 3 andSection 4.3 of 3GPP TR 38.811 V15.0.0 (2018-06) can be referred.

NTN means networks, or segments of networks, using an airborne orspace-borne vehicle to embark a transmission equipment relay node orbase station. In NTN, the following definitions may be used.

-   -   Aerial: an airborne vehicle embarking a bent pipe payload or a        regenerative payload telecommunication transmitter, typically at        an altitude between 8 to 50 km.    -   Airborne vehicles: unmanned aircraft systems (UAS) encompassing        tethered UAS (TUA), lighter than air UAS (LTA), heavier than air        UAS (HTA), all operating in altitudes typically between 8 and 50        km including high altitude platforms (HAPs)    -   Availability: % of time during which the RAN is available for        the targeted communication. The RAN may contain several access        network components among which an NTN to achieve        multi-connectivity or link aggregation.    -   Beam throughput: data rate provided in a beam    -   Bentpipe payload: payload that changes the frequency carrier of        the uplink RF signal, filters and amplifies it before        transmitting it on the downlink    -   Connectivity: capability to establish and maintain        data/voice/video transfer between networks and parts thereof    -   Geostationary Earth orbit (GEO): Circular orbit at 35,786        kilometres above the Earth's equator and following the direction        of the Earth's rotation. An object in such an orbit has an        orbital period equal to the Earth's rotational period and thus        appears motionless, at a fixed position in the sky, to ground        observers.    -   Low Earth orbit (LEO): Orbit around the around Earth with an        altitude between 500 kilometres (orbital period of about 88        minutes), and 2,000 kilometres (orbital period of about 127        minutes).    -   Medium Earth orbit (MEO): region of space around the Earth above        LGO and below GEO.    -   Mobile Services: a radio communication service between mobile        and land stations, or between mobile stations    -   Mobile Satellite Services: A radio communication service between        mobile earth stations and one or more space stations, or between        space stations used by this service; or between mobile earth        stations by means of one or more space stations    -   Non geostationary Satellites: Satellites (LEO and MEO) orbiting        around the Earth with a period that varies approximately between        1.5 hour and 10 hours. It is necessary to have a constellation        of several Non geostationary satellites associated with handover        mechanisms to ensure a service continuity.    -   On Board processing: digital processing carried out on uplink RF        signals aboard a satellite or an aerial.    -   One way latency: time required to propagate through the RAN from        a terminal to the gateway or from the gateway to the terminal.        This is especially used for voice and video conference        applications.    -   Regenerative payload: payload that transforms and amplifies an        uplink RF signal before transmitting it on the downlink. The        transformation of the signal refers to digital processing that        may include demodulation, decoding, re-encoding, re-modulation        and/or filtering.    -   Relay node: Relay of Uu radio interface. The relay function can        take place at Layer 1, 2 or 3.    -   Reliability: probability that the RAN performs in a satisfactory        manner for a given period of time when used under specific        operating conditions. The RAN may contain several access network        components including an NTN to achieve multi-connectivity or        link aggregation.    -   Round trip delay (RTD): time required for a network        communication to travel from a terminal to the gateway or from        the gateway to the terminal and back. This is especially used        for web based applications.    -   Satellite: a space-borne vehicle embarking a bent pipe payload        or a regenerative payload telecommunication transmitter, placed        into LEO typically at an altitude between 500 km to 2000 km, MEO        typically at an altitude between 8000 to 20000 km, or GEO at 35        786 km altitude.    -   Space-borne vehicles: Satellites including LEO satellites, MEO        satellites, GEO satellites as well as highly elliptical orbiting        (HEO) satellites    -   User Connectivity: capability to establish and maintain        data/voice/video transfer between networks and Terminals    -   User Throughput: data rate provided to a terminal

NTN Access Typically Features the Following System Elements:

-   -   NTN terminal: It may refer to directly the 3GPP UE or a terminal        specific to the satellite system in case the satellite doesn't        serve directly 3GPP UEs.    -   A service link which refer to the radio link between the user        equipment and the space/airborne platform. In addition, the UE        may also support a radio link with terrestrial based RAN.    -   A space or an airborne platform embarking a payload which may        implement either a bent-pipe or a regenerative payload        configuration.    -   A bent pipe payload: Radio Frequency filtering, Frequency        conversion and amplification:    -   A regenerative payload: Radio Frequency filtering, Frequency        conversion and amplification as well as demodulation/decoding,        switch and/or routing, coding/modulation. This is effectively        equivalent to having base station functions (e.g. gNB) on board        the space/airborne vehicle    -   Inter satellite/aerial links (ISL) in case of regenerative        payload and a constellation of satellites. ISL may operate in RF        frequency or optical bands.    -   Gateways that connect the satellite or aerial access network to        the core network    -   Feeder links which refer to the radio links between the gateways        and the space/airborne platform

Two types of satellite and aerial access network may be distinguished asfollows.

-   -   Broadband access network serving very small aperture terminals        that can be fixed or mounted on a moving platform (e.g., bus,        train, vessel, aircraft, etc.). In this context, broadband        refers to at least 50 Mbps data rate and even up to several        hundred Mbps (satellite) or even up to several Gbps (aerial) on        the downlink. The service links operate in frequency bands        allocated to satellite and aerial services (Fixed, Mobile) above        6 GHz.    -   Narrow or wide band access network serving terminals equipped        with omni or semi directional antenna (e.g. handheld terminal).        In this context, narrowband refers to less than 1 or 2 Mbps data        rate on the downlink. The service links operate typically in        frequency bands allocated to mobile satellite or aerial services        below 6 GHz.

Also, satellite and aerial systems with ISL or inter-aerial links (IAL)and those without ISL/IAL may be distinguished.

Propagation delay is described.

In the case of bent pipe satellites, one way propagation delay is thesum of feeder link propagation delay and user link propagation delay,thus the propagation delay between Gateway and UE.

In the case of regenerative satellite, one way propagation delay is thesatellite to UE propagation delay.

In both cases the transit time and/or processing time are not taken intoaccount.

In the case of bent pipe satellite, the Round Trip Time is the physicalpath duration of the path: Gateway-Satellite-UE-Satellite-Gateway, thatis in fact twice the one way propagation delay.

In the case of regenerative satellite, the round trip delay is the delaycorresponding to the following path: satellite-UE-satellite.

In the computation, Gateway is set at 5° (TBC) elevation angle, andterminal can be set at various elevation angles, but we consider thatthe reference case is 10° elevation angle for the propagation delaycomputation.

FIG. 10 shows an example of satellite access network (without ISL) witha service link operating in frequency bands above 6 GHz allocated tofixed and mobile satellite services (FSS and MSS) to whichimplementations of the present disclosure is applied.

Referring to FIG. 10, a very small aperture terminals that can be fixedor mounted on a moving platform is connected to a spaceborne platformvia a service link. The spaceborne platform is connected to a gatewayvia a feeder link.

FIG. 11 shows an example of satellite access network (with ISL) with aservice link operating in frequency bands above 6 GHz allocated to FSSand MSS to which implementations of the present disclosure is applied.

Referring to FIG. 11, a very small aperture terminals that can be fixedor mounted on a moving platform is connected to a first spaceborneplatform via a service link. The first spaceborne platform is connectedto a second spaceborne platform via ISL. The second spaceborne platformis connected to a gateway via a feeder link.

FIG. 12 shows an example of satellite access network with a service linkoperating in frequency bands below 6 GHz allocated to MSS to whichimplementations of the present disclosure is applied.

Referring to FIG. 12, a handheld device and/or IoT device is connectedto a spaceborne platform via a service link. The spaceborne platform isconnected to a gateway via a feeder link.

FIG. 13 shows an example of satellite access network which service linkoperates below 6 GHz frequency bands allocated to MSS and complementedwith the terrestrial access network served by the same or independentcore networks to which implementations of the present disclosure isapplied.

Referring to FIG. 13, a handheld device and/or IoT device is connectedto a spaceborne platform via a service link. The spaceborne platform isconnected to a gateway via a feeder link. Furthermore, a handheld deviceand/or IoT device is connected to a terrestrial component via a servicelink. The terrestrial component is connected to core network.

Conditional handover (CHO) has been discussed in LTE and NR to improvehandover robustness. In the CHO procedure, the network can configuremultiple candidate cells with CHO triggering condition to UE via RRCdedicated signalling. UE may perform access to one of the candidatecells which satisfies the CHO triggering condition.

As a way to resolve the above difficulties in NR radio condition, it issuggested to consider handover procedure based on a configured condition(i.e., conditional handover (CHO)). The motivation for the handoverprocedure based on a configured condition is to reduce the time to takenfor transmission of measurement reporting and reception of handovercommand and handover preparation so that it would be possible to reducethe handover failure caused by not receiving handover command at aproper time.

FIG. 14 shows an example of overall procedure for condition basedautonomous handover procedure to which implementations of the presentdisclosure is applied.

In step S1400, the source gNB may provide measurement controlinformation to the UE. In step S1410, the UE may transmit measurementsreports based on the measurement control information.

In step S1420, the source gNB may prepare condition based autonomoushandover procedure with candidate cells (e.g., Cell1 and Cell2 in FIG.14). In step S1430, the source gNB provides handover assistanceinformation to the UE.

The UE is provided with handover assistance information which includesset of candidate cells and conditions (e.g., RSRP) for handover. It maybe possible the network prepares the candidate cells and provide thehandover assistance information without the measurement report from theUE if the network is able to know the trajectory or location of the UEbased on, e.g., location reporting. Additionally, the network maydetermine the set of candidate cells based on the received measurementreport.

There may be a concern on signaling overhead due to earlier triggeringthreshold. Measurement reporting may be reduced if an approach similarto blacklisted cells is introduced. In other words, if the UE reports onone cell, the network may prepare the multiple cells which is inproximity of the reported cell and provide the list of cells which areprepared. Then, the UE may not report on the cells even if the conditionfor measurement reporting is triggered.

The handover assistance information may be cell quality based conditionsand the configuration which may be used in a target cell. The handoverassistance information may include configuration for one or morecandidate cells.

In step S1440, if the UE receives the handover assistance information,the UE initiates to evaluate the conditions for the candidate cell listto determine whether to perform handover procedure to one of thecandidate cells.

In step S1450, if the condition is met, the UE performs connecting tothe prepared target cell.

For this procedure, since the source gNB may not know the exact timingof UE detaching from the source gNB, there may be some unnecessarydownlink transmissions from the network to the UE. To address thisissue, the target gNB may indicate to source gNB that the UE hascompleted handover successfully so that the source gNB does not transmitto the UE anymore. In addition, if the source gNB does not receive theresponse for the transmitted data, the source gNB may not transmit thedata in downlink considering the handover situation.

As s reserving the resource in one or more candidate cell is burdensometo the network, it may be possible for the network to manage theconfiguration efficiently. For instance, based on the timer associatedwith validity of the handover assistance information, the network and

UE may discard the configuration associated with the conditionalhandover. In addition, based on measurement report from the UE, networkmay configure, modify and/or discard the configuration.

Furthermore, if the UE successfully connects to the target cell, thetarget cell may inform to the source cell to discard the reservedconfiguration of the other candidate cell.

Meanwhile, in NTN, CHO could be adapted. As LEO satellites revolvearound the earth every few hours on predictable ephemeris, a cell servedby a LEO satellite may appear to the UE on the ground few minutesperiodically, for example, 10 to 15 minutes.

The baseline of the CHO triggering condition may be cell quality. Inaddition, regarding that the network can predict when a certain LEOsatellite will appear to a UE, absolute validity time period may beconsidered for additional CHO triggering condition. The UE can triggerCHO to a configured candidate cell only if the cell quality condition issatisfied within the absolute validity time period.

As each cell can be configured with absolute validity time period, it ispossible that multiple NTN cells may simultaneously satisfy the CHOtriggering condition. If multiple cells satisfy the CHO triggeringcondition, selection of which cell to perform CHO shall be determined.Therefore, studies for conditional handover based on the service time ofcandidate cells in a wireless communication system is required.

Hereinafter, a method for conditional handover based on the service timeof candidate cells in a wireless communication system, according to someembodiments of the present disclosure, will be described with referenceto the following drawings.

The following drawings are created to explain specific embodiments ofthe present disclosure. The names of the specific devices or the namesof the specific signals/messages/fields shown in the drawings areprovided by way of example, and thus the technical features of thepresent disclosure are not limited to the specific names used in thefollowing drawings. Herein, a wireless device may be referred to as auser equipment (UE).

FIG. 15 shows an example of a method for conditional handover based onthe service time of candidate cells in a wireless communication system,according to some embodiments of the present disclosure. In particular,FIG. 15 shows an example of a method for performed by a wireless device.

In step 1501, a wireless device may receive, from a network, handoverconfiguration including information related to candidate cells to bemeasured and service time of each of the candidate cells.

For example, the candidate cells may include at least one of anon-terrestrial networks (NTN) cell.

For example, the information related to the candidate cells may includelist of the candidate cells.

For example, the handover configuration may include information on thehandover condition.

In step 1502, a wireless device may perform measurement on the candidatecells.

For example, a wireless device may determine that each of the candidatecells is met a handover condition based on the measurement.

For example, the handover condition may be include in the handoverconfiguration. For example, the handover configuration may include atleast one of a handover condition.

For example, a handover condition may related to a cell quality. Forexample, a cell may be met the handover condition, when a cell qualityof the cell is equal to or higher than a cell quality threshold. Inother words, the each of the candidate cells may be determined to be metthe handover condition based on that cell quality of the each of thecandidate cells is equal to or higher than a cell quality threshold. Forexample, the cell quality threshold may be included in the handoverconfiguration.

For example, a handover condition may related to a service time. Forexample, a cell may met the handover condition when the measured timepoint of the cell is within the service time of the cell.

For example, a cell may be met the handover condition, when a remainingservice time of the cell is equal to or higher than a minimum timethreshold. In other words, the each of the candidate cells may bedetermined to be met the handover condition based on that the servicetime of each of the candidate cells is equal to or higher than a minimumtime threshold. For example, the minimum time threshold may be includedin the handover configuration.

For example, a cell may be met the handover condition, when a remainingservice time of the cell is lower than a maximum time threshold. Inother words, the each of the candidate cells is determined to be met thehandover condition based on that the service time of each of thecandidate cells is lower than a maximum time threshold. For example, themaximum time threshold may be included in the handover configuration.

In step 1503, a wireless device may select a cell among the candidatecells based on the service time of each of the candidate cells.

For example, a wireless device may select the cell among the candidatecells based on remaining time of the service time of each of thecandidate cells from a specific time point. For example, the remainingtime may be determined as time a period from the specific time point toend of the absolute service time.

For example, the specific time point may be a time point when themeasurement is performed. In other words, a wireless device may performthe measurement at the specific time point and determine the remainingservice time of each of the candidate cells from the specific time pointbased on the handover configuration.

For example, a wireless device may select a cell among the candidatecells which are met the handover condition. For example, a wirelessdevice may determine a set of candidate cells which are met the handovercondition. A wireless device may select a cell for handover among theset of candidate cells.

In step 1504, a wireless device may perform handover to the selectedcell.

According to some embodiments of the present disclosure, a wirelessdevice may be in communication with at least one of a user equipment, anetwork, or an autonomous vehicle other than the wireless device.

FIG. 16 shows an example of a method for conditional handover based onthe service time of candidate cells in a wireless communication system,according to some embodiments of the present disclosure. In particular,FIG. 16 shows an example of a method for selection of NTN cells toperform CHO among multiple cells satisfying the condition.

For example, if a UE is provided with CHO configuration and if multipleNTN cells simultaneously satisfy the CHO triggering condition, the UEmay select the cell with longest remaining absolute validity timeperiod.

Referring to FIG. 16, in step 1601, a UE may acquire CHO configuration.For example, the UE may be provided with CHO configuration, when the UEis in connected mode,

For example, CHO configuration may include list of candidate cells toexecute CHO.

For example, each candidate cell in the CHO configuration may beconfigured with CHO triggering condition.

For example, in the CHO triggering condition, cell quality threshold maybe configured.

For example, in the CHO triggering condition, absolute validity timeperiod may be configured.

For example, absolute validity time period may include minimum absolutetime threshold and/or maximum absolute time threshold.

In step 1602, the UE may perform measurement on cells. For example, theUE may perform measurement on the cells in the list included in the CHOconfiguration.

In step 1603, the UE may select the cell with longest remaining absolutevalidity time period among the multiple cells satisfying the CHOtriggering condition. For example, if multiple cells satisfy the CHOtriggering condition at a same time, the UE may select the cell withlongest remaining absolute validity time period among the multiple cellssatisfying the CHO triggering condition.

For example, CHO triggering condition for a cell is satisfied ifmeasured cell quality of the cell is higher than the configured cellquality threshold and the measured time point of the cell is within theabsolute validity time period of the cell.

For example, the remaining absolute validity time period is timedifference between the measured time point of the cell quality andmaximum absolute time threshold.

In step 1604, the UE may perform CHO to the selected cell.

FIG. 17 shows a diagram of an example of method for conditional handoverbased on the service time of candidate cells in a wireless communicationsystem, according to some embodiments of the present disclosure.

For example, a UE may acquire CHO configuration. The CHO configurationmay include the cell list including the cells A, B, C, and D. The CHOconfiguration may include information related to the absolute validitytime period (or service time) for the cells A, B, C, and D.

In FIG. 17, it is assumed that the absolute validity time periods in theCHO configuration are provided for the cells A, B, C and, D. Forexample, black boxes in the time axis may represent the configuredabsolute validity time period for each cell.

At the time point 1, UE may check the conditions included in the CHOconfiguration. For example, at the time point 1, UE may measure cellquality of the cells.

The cells A, B, and C may satisfy the condition included in the CHOconfiguration. For example, the measured cell quality of cell A, B, andC is higher than the threshold. In addition, cells A, B, and C are validat the time point 1. In other words, the absolute validity time periodsof cells A, B, and C may contain the time point 1. In this case, UE mayselect the cell B, since cell B has the longest remaining absolutevalidity time period. Then, the UE may trigger CHO to the cell B.

The present disclosure can have various advantageous effects.

According to some embodiments of the present disclosure described withreference to FIGS. 15 and 17, a wireless device may perform conditionalhandover to the NTN cell efficiently.

For example, a wireless device may consider the available service timeas one condition of the conditional handover.

For example, a wireless device could determine a cell having the longestavailable service time among the candidate cells.

For example, a wireless device could select a cell having the longestservice time among the candidate cells.

For example, if cell quality condition and absolute validity time periodcondition are both configured for triggering CHO, a wireless devicecould select a cell to trigger CHO whose available NTN service time isthe longest.

Advantageous effects which can be obtained through specific embodimentsof the present disclosure are not limited to the advantageous effectslisted above. For example, there may be a variety of technical effectsthat a person having ordinary skill in the related art can understandand/or derive from the present disclosure. Accordingly, the specificeffects of the present disclosure are not limited to those explicitlydescribed herein, but may include various effects that may be understoodor derived from the technical features of the present disclosure.

Claims in the present disclosure can be combined in a various way. Forinstance, technical features in method claims of the present disclosurecan be combined to be implemented or performed in an apparatus, andtechnical features in apparatus claims can be combined to be implementedor performed in a method. Further, technical features in method claim(s)and apparatus claim(s) can be combined to be implemented or performed inan apparatus. Further, technical features in method claim(s) andapparatus claim(s) can be combined to be implemented or performed in amethod. Other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A method performed by a wireless device in awireless communication system, the method comprising, receiving, from anetwork, handover configuration including information related tocandidate cells to be measured and service time of each of the candidatecells; performing measurement on the candidate cells; selecting a cellamong the candidate cells based on the service time of each of thecandidate cells; and performing handover to the selected cell.
 2. Themethod of claim 1, wherein the candidate cells includes anon-terrestrial networks (NTN) cell.
 3. The method of claim 1, whereinthe method further comprises, determining whether each of the candidatecells is met a handover condition based on the measurement, wherein thehandover configuration includes information on the handover condition.4. The method of claim 3, wherein the cell is selected among thecandidate cells which are met the handover condition.
 5. The method ofclaim 3, wherein the each of the candidate cells is determined to be metthe handover condition based on that cell quality of the each of thecandidate cells is equal to or higher than a cell quality threshold. 6.The method of claim 3, wherein the each of the candidate cells isdetermined to be met the handover condition based on that the servicetime of each of the candidate cells is equal to or higher than a minimumtime threshold.
 7. The method of claim 3, wherein the each of thecandidate cells is determined to be met the handover condition based onthat the service time of each of the candidate cells is lower than amaximum time threshold.
 8. The method of claim 1, wherein the cell isselected among the candidate cells based on remaining time of theservice time of each of the candidate cells from a specific time point.9. The method of claim 8, wherein the measurement on the candidate cellsis performed at the specific point.
 10. The method of claim 1, whereinthe wireless device is in communication with at least one of a userequipment, a network, or an autonomous vehicle other than the wirelessdevice.
 11. A wireless device in a wireless communication systemcomprising: a transceiver; a memory; and at least one processoroperatively coupled to the transceiver and the memory, and configuredto: control the transceiver to receive, from a network, handoverconfiguration including information related to candidate cells to bemeasured and service time of each of the candidate cells; performmeasurement on the candidate cells; select a cell among the candidatecells based on the service time of each of the candidate cells; andperform handover to the selected cell.
 12. The method of claim 11,wherein the at least one processor is further configured to, determinewhether each of the candidate cells is met a handover condition, whereinthe handover configuration includes information on the handovercondition.
 13. The method of claim 12, wherein the cell is selectedamong the candidate cells which are met the handover condition.
 14. Themethod of claim 11, wherein the cell is selected among the candidatecells based on remaining time of the service time of each of thecandidate cells from a specific time point.
 15. The method of claim 14,wherein the measurement on the candidate cells is performed at thespecific point.
 16. A non-transitory computer-readable medium havingstored thereon a plurality of instructions, which, when executed by aprocessor of a wireless device, cause the wireless device to: receive,from a network, handover configuration including information related tocandidate cells to be measured and service time of each of the candidatecells; perform measurement on the candidate cells; select a cell amongthe candidate cells based on the service time of each of the candidatecells; and perform handover to the selected cell.